Investigating the Drivers of Dry Season Rainfall over Eastern Africa

Abstract: Rainfall events during the January-February dry season over Eastern Africa have significant impact upon society, particularly when they lead to, or exacerbate, ongoing flooding (as in Kenya in 2020 and 2022). Populations across Eastern Africa do not expect rainfall to occur during the January-February dry season, and a lack of preparedness can exacerbate impacts when heavy rainfall does occur. Whilst recent dry season rainfall across Eastern Africa has severely impacted livelihoods and communities, the mechanisms controlling such rainfall are poorly understood, since the majority of previous research has focussed upon the climatological wet seasons. Here, we explore drivers of dry season rainfall over Eastern Africa.

Dry season rainfall over Eastern Africa is found to be linked to an upper-level ridge-trough pattern over the Mediterranean. The presence of a ridge in the central Mediterranean and trough in the Eastern Mediterranean leads to westerly wind anomalies across Central Africa, which enhances moisture transport into Eastern Africa and leads to higher specific humidity and rainfall over the region. Dry season rainfall is further exacerbated by phases 2-4 of the MJO. These findings will improve future forecasts of dry season rainfall over Eastern Africa, which will enhance preparedness for future rainfall events.  Furthermore, climate projections from CMIP5 and CMIP6 models indicate enhanced dry season rainfall over Eastern Africa under future climate change. Improving our understanding of drivers of present-day dry season rainfall will support our understanding of future rainfall changes.

Biography: Caroline is a Lecturer in Climate Change at Cardiff University. Her research is around climate variability and change over Africa, with a specific interest in exploring variability and changes in the seasonal cycle of rainfall over Africa, including recent trends, current variability, and future projected changes. caroline has worked on methodologies for characterising the seasonal cycle of precipitation across Africa and the tropics, and used these methodologies for a range of applications.